Induction of somatic embryogenesis and plant regeneration in the tropical timber tree Spanish red cedar [Cedrela odorata L. (Meliaceae)]

Spanish red cedar (Cedrela odorata L.) is a tropical timber tree native to the Americas from southern Mexico to northern Argentina. Commercial plantations are scarce and, consequently, natural populations are overexploited. Traditional propagation practices for the establishment of large-scale plantations have had limited success in this species due to the relative scarcity of seeds, its broad genetic diversity and the lack of domesticated varieties. In vitro clonal propagation provides an effective method to overcome this situation and increase the yield of commercial plantations through the rapid multiplication of elite materials. Somatic embryogenesis (SE) is one of the most promising strategies for tree propagation due to the possibility of producing artificial seeds, the ability to store and rapidly mobilize germplasm and the opportunity for genetic manipulation. We report here the induction of indirect SE in C. odorata from calli derived from immature zygotic embryos after 12 weeks of culture. Macroscopic, histological, and scanning electron microscopic analyses of the calli revealed the presence of embryogenic cell clusters that formed cotyledonary embryos with clear bipolar structures and no vascular connections with the mother tissue. Different media preparations containing combinations of diverse auxins and cytokinins are known to have different effects on the type and frequency of embryogenic structures. Embryo conversion was achieved using an MS-based medium [Murashige T, Skoog F (1962) Physiol Plant 15:473-497, 1962] supplemented with abscisic acid, and transfer to soil was successful at a rate of 75%. The method described here provides a basis for optimizing the clonal propagation and genetic manipulation of this valuable species.